bpo-36051: Drop GIL during large bytes.join() (GH-17757)

Improve multi-threaded performance by dropping the GIL in the fast path
of bytes.join. To avoid increasing overhead for small joins, it is only
done if the output size exceeds a threshold.
diff --git a/Misc/ACKS b/Misc/ACKS
index 7e4b81b..f3e3680 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1106,6 +1106,7 @@
 Doug Mennella
 Dimitri Merejkowsky
 Brian Merrell
+Bruce Merry
 Alexis Métaireau
 Luke Mewburn
 Carl Meyer